My strong suspicion is that that well is supposed to be draining effectively into the sump pit.
In my house I have 4 window wells with hardware (corrugated metal and window frame) that is identical to your. Two of the wells have catchments that drain into the foundation drain lines that lead to the sump pit. They have a grated cover that is just a touch below level with the top of the coarse gravel in the well. The other two have no exposed catchment and they are intended to drain either directly through the gravel or through a buried riser pipe into the foundation drain line below.
I am not sure why some are drained and others not, I suspect it has to do with the slope of the foundation drain line below, or maybe with the way the architect/engineer believed the water might come of different parts of the roof. I have never had them flood, even when they were completely surrounded by standing water, the drainage to the sump is direct.
At any rate, your window wells would have been designed to drain water under worst-case conditions which leaves two possibilities:
1-The designer did not accurately estimate what the worst-case water ingress was. Perhaps once in a century flooding or failure to account for ground water saturation from closely situated neighbor whose downspout is close to your window.
2-Something is not as the designer intended. Maybe something is occluding a part of your foundation drain lines. Maybe excessive settling has messed up the slope of the lines so that your well is now at a low spot.
Bottom line is that the well is not really intended to keep water out in the first place, but rather to be able to drain it freely.
It sounds like you have already looked at your downspouts and sump pump. How full is the pit getting? Does it run almost continously? Can you see where the foundation lines drain into the pit and how much water is flowing from the line that would drain that well? Is the water ejected from the sump so that it cannot flow back to the foundation?
My understanding is that if your drain system is working, water should never really be sitting at that level against your foundation, so that even if sealing the well to the house helped, it might just be treating the symptom and not the bigger issue.
I would dig,carefully, in the bottom of that well to try to find a drain. If the material you are digging through is largely dirt and fines, I would replace it with the appropriate grade of gravel for draining. If you find a riser, try to flush it out maybe a leaf blower+duct tape or possibly a snake. In a <30yo house I would expect to be able to find information on the existing sump system somewhere.
IDK if its possible or appropriate to dig all the way to the foundation drain line, which I believe is usually at or below the top of the basement floor, but if you did I would think you could splice in a tee and riser up to a catchment for the well.
Last, if a drain could not be found, I would consider setting up a compact sump and pit down in the bottom of that well.